Modem vehicular and automotive systems are increasingly using sensors to determine whether there is adequate air pressure in tires. In such systems a pressure sensor unit is arranged on the tire to monitor the tire pressure and detect a sudden pressure drop. The measured pressure or measures pressure variation is then transmitted to a control circuitry within the vehicle using a radio frequency data link.
Conventional systems normally use a battery power source with a life requirement of many years. Power from the battery is consumed during pressure and temperature measurements, RF communication and from the overall standby time. To increase the battery's lifespan various power management concepts are known to minimize consumption. Some of them are based on detection of vehicle motion.
When tires are changed, the unit of the pressure measurement system within the vehicle has to identify the new pressure sensors and allocate specified tire position to the newly identified sensor. Such identification often uses a bidirectional communication, where the control circuit within the vehicle sends an identification request to the pressure sensors within the tires. The pressure sensors identify themselves in response to the received request. Such bidirectional communication can also be used to set how frequently the pressure measurement is transmitted in case of a close surveillance of the tire pressure. However, a bidirectional communication requires one or several transmitters in the car chassis as well as a receiver for each sensing unit. This is a significant cost factor and consumes additional power for transmitter and receiver.
It is desirable to provide a method for demand driven pressure transmission over a unidirectional transmission link. There is also a need to provide a method for determining a tire position without the requirement of an additional receiver in the pressure sensing unit.